TCP memory pressure question

When a Linux machine has reached the tcp_mem limit, what will happen to
'write's on non-blocking sockets? Will they block until more TCP memory is available? Will they return an error code? ENOMEM?

If it varies by kernel version, details about different versions would be
extremely helpful. I'm most interested in late 2.4 kernels.

Thanks in advance.

Quoted 8 lines

When a Linux machine has reached the tcp_mem limit, what will happen to 'write's on non-blocking sockets? Will they block until more TCP memory is available? Will they return an error code? ENOMEM?

If it varies by kernel version, details about different versions would be extremely helpful. I'm most interested in late 2.4 kernels.

Thanks in advance.

Returns EAGAIN.
Fairly static ~late 2.4.